Homework 4, Newton's laws 23-24-problems

peacock (ip6239) – Homework 4, Newton’s laws 23-24 – tejeda – (KayaAPHY1 1) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. You will have approximately two weeks to complete this homework assignment. Collab- oration on homework is encouraged. How- ever, you must submit your own responses, and you may be required to show your in- dependent work to your HS Instructor. You are expected to access Quest daily to progress through this homework assignment. 001(part1of2)10.0points A book is at rest on an incline as shown below. A hand, in contact with the top of the book, produces a constant force F hand vertically downward. F hand Book The following figures show several attempts at drawing free-body diagrams for the book. Which figure has the correct directions for each force? The magnitudes of the forces are not necessarily drawn to scale. 1. F N F hand F f F g 2. F g F f F hand F N 3. F g F hand F N F f 4. F g F f F N F hand 5. F g F N F f F hand 6. F g F hand F N F f 7. F g F hand F f F N

peacock (ip6239) – Homework 4, Newton’s laws 23-24 – tejeda – (KayaAPHY1 1) 2 8. F N F f F g F hand 002(part2of2)10.0points For the normal force exerted on the book by the wedge in the diagram, which force(s) complete(s) the force pair for Newton’s third law (action-reaction)? 1. the component of gravity pointing per- pendicular to the surface of the incline 2. the component of gravity pointing parallel to the surface of the incline 3. the pull of the earth on the book 4. the sum of the component of gravity per- pendicular to the surface of the incline and the component of F hand perpendicular to the surface of the incline 5. the normal force exerted on the wedge by the book 6. the component of F hand pointing perpen- dicular to the surface of the incline 7. the pull of the book on the earth 003(part1of2)10.0points A balloon is waiting to take off. As seen in the figure below, the balloon’s basket sits on a platform which rests on the ground. The balloon is pulling up on the basket, but not hard enough to lift it off the platform. platform basket ground balloon What is the free-body diagram for the plat- form? Some parallel vectors are offset hori- zontally for clarity. 1. F ground on plat F grav on plat F bask on plat 2. F bal on plat F plat on ground F grav on plat 3. F bal on plat F grav on plat 4. F bal on bask F grav on bask F grav on plat 5. F plat on bask F plat on ground F grav on plat 004(part2of2)10.0points What is the free body diagram for the bas- ket? Again some parallel vectors are offset horizontally for clarity. 1. F bask on plat F bask on bal F grav on bask 2. F bal on bask F grav on bask 3. F grav on bask F bal on bask F plat on bask

peacock (ip6239) – Homework 4, Newton’s laws 23-24 – tejeda – (KayaAPHY1 1) 4 4. The truck exerts the same amount of force on the car as the car exerts on the truck. 5. None of the answers correctly describes the situation. 6. Neither exerts a force on the other; the car gets smashed simply because it is in the way of the truck. 011 10.0points Consider a horse pulling a buggy. Is the following statement true? The weight of the horse and normal force exerted by the ground on the horse constitute an interaction pair that are always equal and opposite according to Newton’s third law. 1. no 2. yes 012 10.0points A book rests on the shelf of a bookcase. The reaction force to the force of gravity acting on the book is 1. The force of the shelf holding the book up. 2. None of these. 3. The force exerted by the book on the earth. 4. The frictional force between book and shelf. 5. The weight of the book. 013 10.0points When you drop a 0 . 39 kg apple, Earth exerts a force on it that accelerates it at 9 . 8 m / s 2 to- ward the earth’s surface. According to New- ton’s third law, the apple must exert an equal but opposite force on Earth. If the mass of the earth 5 . 98 × 10 24 kg, what is the magnitude of the earth’s acceleration toward the apple? Answer in units of m / s 2 . Answer in units of m / s 2 . 014 10.0points Consider the following system, where F = 40 N, m = 6 kg, and M = 9 kg M m F What is the magnitude of the force with which one block acts on the other? 1. 16 N 2. 40 N 3. 60 N 4. None of these 5. 24 N 6. 26 . 6667 N 015(part1of2)10.0points A light, inextensible cord passes over a light, frictionless pulley with a radius of 11 cm. It has a(n) 12 kg mass on the left and a(n) 6 . 6 kg mass on the right, both hanging freely. Initially their center of masses are a vertical distance 1 . 8 m apart. The acceleration of gravity is 9 . 8 m / s 2 . 1 . 8 m 11 cm ω 12 kg 6 . 6 kg At what rate are the two masses accelerat-

peacock (ip6239) – Homework 4, Newton’s laws 23-24 – tejeda – (KayaAPHY1 1) 5 ing when they pass each other? Answer in units of m / s 2 . Answer in units of m / s 2 . 016(part2of2)10.0points What is the tension in the cord when they pass each other? Answer in units of N. Answer in units of N. 017(part1of2)10.0points An elevator accelerates upward at 1 . 2 m / s 2 . The acceleration of gravity is 9 . 8 m / s 2 . What is the upward force exerted by the floor of the elevator on a(n) 96 kg passenger? Answer in units of N. Answer in units of N. 018(part2of2)10.0points If the same elevator accelerates downwards with an acceleration of 1 . 2 m / s 2 , what is the upward force exerted by the elevator floor on the passenger? Answer in units of N. Answer in units of N. 019(part1of3)10.0points You are driving at the speed of 28 . 5 m / s (63 . 7663 mph) when suddenly the car in front of you (previously traveling at the same speed) brakes and begins to slow down with the largest deceleration possible without skid- ding. Considering an average human reaction, you press your brakes 0 . 493 s later. You also brake and decelerate as rapidly as possible without skidding. Assume that the coefficient of static friction is 0 . 886 between both cars’ wheels and the road. The acceleration of gravity is 9 . 8 m / s 2 . Calculate the acceleration of the car in front of you when it brakes. Answer in units of m / s 2 . Answer in units of m / s 2 . 020(part2of3)10.0points Calculate the braking distance for the car in front of you. Answer in units of m. Answer in units of m. 021(part3of3)10.0points Find the minimum safe distance at which you can follow the car in front of you and avoid hitting it (in the case of emergency braking described here). Answer in units of m. Answer in units of m. 022(part1of3)10.0points A block is at rest on the incline shown in the figure. The coefficients of static and ki- netic friction are μ s = 0 . 45 and μ k = 0 . 38, respectively. The acceleration of gravity is 9 . 8 m / s 2 . 25 kg μ 22 ◦ What is the frictional force acting on the 25 kg mass? Answer in units of N. Answer in units of N. 023(part2of3)10.0points What is the largest angle which the incline can have so that the mass does not slide down the incline? Answer in units of ◦ . Answer in units of ◦ . 024(part3of3)10.0points What is the acceleration of the block down the incline if the angle of the incline is 29 ◦ ? Answer in units of m / s 2 . Answer in units of m / s 2 .